A liquid supply apparatus is used for coating a surface of a semiconductor wafer, a glass substrate for liquid crystal or the like with a chemical solution such as a photoresist solution. In one type of the liquid supply apparatus like this, as described in Japanese Patent Application Laid-Open Publication No. 2006-266250 (Patent Document 1), a bellows for expanding and contracting a pump chamber is provided. For the expansion and contraction of the bellows, the apparatus has a syringe body in which a piston rod, that is, a plunger is inserted so as to be reciprocatable in an axial direction, and the bellows is driven by expanding and contracting a syringe chamber filled with indirect liquid by the piston rod.
A liquid supply apparatus of a type which performs a pumping operation by reciprocating the piston rod is called a piston type or a syringe type. A chemical solution such as a photoresist solution is suctioned into the syringe chamber by expanding the syringe chamber and discharged by contracting the syringe chamber, thereby coating a coating target with the liquid discharged from the syringe chamber.